In many industrial environments, it is desirable to exclude persons from selected assembly/manufacturing or other areas to prevent injuries to persons by equipment operating within the area. To effect such exclusion, referring to FIG. 3, a barrier 20, for example a fence, is erected around such an area. The fence normally includes a gate 22 hinged to the fence 20 for providing access to and from the manufacturing area. An electrical female receptacle 24 is attached to a fixed end or post 26 of the fence 20. Electrically and mechanically coupled to the receptacle 24 is a male plug 28 which is also connected to one end of a flexible cable or chain 30. The other end of the chain 30 is rigidly connected to the gate 22 at a location proximate a portion or side of the gate 22 that must be moved in order to enter or leave the area inside a perimeter of the fence. Referring to FIG. 4, the plug 28 is often referred to as a shorting plug because its pins 32 are internally shorted together. Pin sockets 34 inside the receptacle 24 are electrically connected to wires or leads 36. The pin sockets 34 receive the pins 32 of the plug 28 when the plug 28 is mechanically connected to the receptacle 24, thereby providing continuity in a circuit to which the wires 36 are connected. For example, the wires 36 may be connected to one side of a power supply 38 that provides power to manufacturing equipment 40.
Thus, with the gate 22 in its illustrated closed position in FIG. 3 and with the receptacle 24 electrically and mechanically coupled to the plug 28, a closed circuit exists from the power supply 38 and in a circuit formed by the wires 36, the receptacle 24, the shorted pins 32 in the plug 38 and the manufacturing equipment 40. Prior to opening the gate 22, the plug 28 must be disconnected from the receptacle 24, thereby interrupting the continuity of the above-described closed circuit. Thus, with the plug 28 disconnected from the receptacle 24, it is not possible for the power supply 38 to supply power to the manufacturing equipment; and the plug 28 and receptacle 24 function as a manually operable electrical interlock or switch. The gate 22 is then opened, and persons can enter within the perimeter of the fence with little risk of the equipment therein being operated without their knowledge. The receptacle 24 and plug 28 are commercially available as Part Nos. 22801 and 22804, respectively, from Brad Harrison, a David Woodhead Company.
Thus, the known receptacle 24 and plug 28 operate effectively to break circuit continuity prior to the gate 22 being opened. As long as the gate 22 remains open, the plug and receptacle cannot be connected; and the manufacturing equipment within the fence perimeter remain inoperable. However, there is one problem with the known plug and receptacle connector. The manufacturing areas inside the perimeter of the fence 20 may be quite large, and further, the manufacturing equipment within the fence perimeter often hide the presence of persons within the perimeter of the fence. In addition, ambient noise within the manufacturing area often distorts and hides vocal calls and warnings. Thus, it is possible that the gate 22 may be closed and the receptacle 24 and plug 28 reconnected while a person remains within the perimeter of the fence.
Therefore, there is a need for an improved electrical connector that prohibits a connection of the connector if a person remains within the perimeter of the fence.